This invention relates to stereo phonograph cartridges in general, and more particularly to an improved stereo phonograph cartridge using a unique coupling method to permit direct coupling between stylus signal motions and transducers with minumum distortion of the record groove modulation.
The need for highly accurate phonograph cartridges which will faithfully reproduce the record groove modulation is well recognized. Over the years, the demands placed on cartridges have steadily been increased. Starting with the improved characteristics needed for long-playing records, then the further improvements needed for stereo records, these demands have steadily increased until now even more stringent requirements must be met for discreet four channel recordings. To provide faithful reproduction of record groove modulations, particularly on these latter types of records, it is necessary that the stylus have an extremely low mechanical impedence, allowing it to faithfully follow the complex and minute groove modulations at a very low stylus force. That these factors become particularly critical for performance over a frequency range of from 0 to 50 Khz and the associated reduction in stylus contact point radius required by discreet four channel recordings is easily recognized. For proper performance in such a discreet four channel system, the phonograph cartridge should have half the mechanical impedence and a linear transducer function up to twice the upper frequency limit as compared to the ordinary stereo performance. Thus, it is clear that improved cartridges are required if these newer discreet four channel recordings are to be reproduced with the same fidelity as ordinary stereo recordings now produced.